A tow truck pulls a car 5.00 km along a horizontal roadway using a cable having a tension of 850 N. (a) How much work does the cable do on the car if it pulls horizontally? If it pulls at 35.0° above the horizontal? (b) How much work does the cable do on the tow truck in both cases of part (a)? (c) How much work does gravity do on the car in part (a)?
Solution 2E Step 1: a) Work done, W = F . S = FS cos If the truck pulls the car horizontally, the direction of motion and direction of force will be same. Hence, = 0° Therefore, W = FS cos 0 = FS (cos 0 = 1) F = 850 N, S = 5 km = 5000 m W = 850 N × 5000 m = 4250000 J = 4 250 kJ If = 35° W ’ = FS cos 35 cos 35 = 0.8192 W ’ = 0.8192 FS That is, W ’ = 0.8192 × 4250 kJ = 3481.6 kJ Step 2: b) The cable does - 4250 kJ of work on the truck if it is pulled horizontally and - 3481.6 kJ of work if it is pulled at an angle 35° on the truck.